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Journal articles on the topic 'Enantiomers - NMR Spectra'

Author: Grafiati

Published: 4 June 2021

Last updated: 6 September 2023

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1

Szabó-Szentjóbi, Hajnalka, Anna Márton, Dávid Pál, et al. "Synthesis, Fluorescence and NMR Spectroscopic Studies of a Novel Phosphinoxido-18-crown-6 Ether Containing an Anthracene Fluorophore Unit." Periodica Polytechnica Chemical Engineering 64, no. 1 (2019): 37–45. http://dx.doi.org/10.3311/ppch.14646.

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The synthesis of the (R,R) and (S,S) enantiomers of a new enantiopure monophospha-18-crown-6 ether (1), which contains an anthracene fluorophore unit and methyl groups at its stereogenic centers, was accomplished. The structure of one enantiomer ((S,S)-1) was studied using one-dimensional (1H, 13C{1H}, and 31P{1H}) and two-dimensional NMR spectra. Because (R,R)-1 and (S,S)-1 can act as new fluorescent chemosensors, we examined their enantiomeric differentiation abilities toward the enantiomers of protonated chiral primary amines and amino acid esters (PEA, 1-NEA, PGME, PAME) using UV-Vis and f

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2

Labuta, Jan, Shinsuke Ishihara, Daniel T. Payne, et al. "Estimation of Enantiomeric Excess Based on Rapid Host–Guest Exchange." Chemosensors 9, no. 9 (2021): 259. http://dx.doi.org/10.3390/chemosensors9090259.

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Chiral molecules possess enantiomers that have non-superimposable chemical structures but exhibit identical nuclear magnetic resonance (NMR) spectra. This feature prevents the use of NMR spectroscopic methods for the determination of enantiomeric excesses (ee) of chiral molecules, using simple mixtures of their enantiomers. Recently, however, it was reported that the addition of a symmetrical prochiral molecule (a reporter or host) into a solution of chiral analyte can lead to estimation of ee through interactions involving rapid exchange of the chiral analyte (guest) in the formed host–guest

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3

Klika, Karel D. "Chiral Solid Solutions for the NMR Analysis of Enantiomers: A Potential New Approach to Chiral Analysis." Journal of Spectroscopy 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/970654.

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Differences between the solid-state13C CP-MAS NMR spectra of holemic samples of the two enantiomers of 2,2′-dihydroxy-1,1′-binaphthyl (binol) were not sufficiently emphatic to reliably distinguish them, though they are readily distinguishable from the spectrum of the bimate of the compound crystallized from an equimatic sample. Inducing an additional chiral environment by cocondensation with sucrose as a chiral selector (CS) provided a method to yield differential spectra for the two enantiomers and thus effect enantiodifferentiation by way of solid-state NMR using weak interactions from a CS.

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4

Cao, Fei, Li Pan, Wenbin Gao, Yunfeng Liu, Caijuan Zheng, and Yahui Zhang. "Structure Revision and Protein Tyrosine Phosphatase Inhibitory Activity of Drazepinone." Marine Drugs 19, no. 12 (2021): 714. http://dx.doi.org/10.3390/md19120714.

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From the marine-derived fungus Penicillium sumatrense (Trichocomaceae), a pair of enantiomers [(+)-1 and (−)-1] were isolated with identical 1D NMR data to drazepinone, which was originally reported to have a trisubstituted naphthofuroazepinone skeleton. In this study, we confirmed the structures of the two enantiomers as drazepinone and revised their structures by detailed analysis of extensive 2D NMR data and a comparison of the calculated 13C chemical shifts, ECD, VCD, and ORD spectra with those of the experiment ones. (+)-1 and (−)-1 were evaluated for their PTP inhibitory activity in vitr

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5

Mamantov, Andrew. "1-Norbornyl cation may be in equilibrium with 2-norbornyl cation." Progress in Reaction Kinetics and Mechanism 45 (August 22, 2019): 146867831986131. http://dx.doi.org/10.1177/1468678319861319.

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New 1H and 13C NMR 400 MHZ spectra of the 2-Nb cation under stable ion conditions, for example, in SbF5/SO2F2/SO2ClF, −80 oC, show besides the usual 1H NMR resonances at δ 4.93, 2.82, 1.85, the never before seen singlet, δ 9.63, and doublet, δ 2.97 (J2,6 = 16.6 Hz), ratio 1.00 : 1.07, proposed to be due to resonance-stabilized bridgehead 1-Nb cationic enantiomers in equilibrium with 2-Nb cation. The corresponding 13C proton-coupled NMR spectrum, −80 oC, has a C3,5,7 triplet, δ 30.45, J(CH) = 139.14 Hz, and C4 doublet, δ 37.7, J(CH) = 154.54 Hz. The C1,2,6 absorption, δ 91.04 is relatively broa

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6

Baumann, Andreas, Alicja Wzorek, Vadim A. Soloshonok, Karel D. Klika, and Aubry K. Miller. "Potentially Mistaking Enantiomers for Different Compounds Due to the Self-Induced Diastereomeric Anisochronism (SIDA) Phenomenon." Symmetry 12, no. 7 (2020): 1106. http://dx.doi.org/10.3390/sym12071106.

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The NMR phenomenon of self-induced diastereomeric anisochronism (SIDA) was observed with an alcohol and an ester. The alcohol exhibited large concentration-dependent chemical shifts (δ’s), which initially led us to erroneously consider whether two enantiomers were in fact atropisomers. This highlights a potential complication for the analysis of chiral compounds due to SIDA, namely the misidentification of enantiomers. A heterochiral association preference for the alcohol in CDCl3 was determined by the intermolecular nuclear Overhauser effect (NOE) and diffusion measurements, the same preferen

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7

Krečmerová, Marcela, Miloš Buděšínský, Milena Masojídková, and Antonín Holý. "Synthesis of Optically Active N6-Alkyl Derivatives of (R)-3-(Adenin-9-yl)-2-hydroxypropanoic Acid and Related Compounds." Collection of Czechoslovak Chemical Communications 68, no. 5 (2003): 931–50. http://dx.doi.org/10.1135/cccc20030931.

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Reaction of ethyl (R)-oxiranecarboxylate (2a) with various nucleobases (adenine, 6-chloropurine, thymine, cytosine, N6-benzoyladenine, 4-methoxy-5-methylpyrimidin-2(1H)-one and 4-methoxypyrimidin-2(1H)-one) afforded ethyl 3-substituted-2-hydroxypropanoates 4-10. Enantioselectivity of this reaction is dependent on the type of the base: 6-chloropurine, N6-benzoyladenine, 4-methoxy-5-methylpyrimidin-2(1H)-one, thymine and cytosine gave optically pure R enantiomers. In other cases, partial or complete racemization occurred. Optically pure ethyl (R)-3-(6-chloropurin-9-yl)-2-hydroxypropanoate (5a) w

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8

Strašák, Milan, Milena Kederová, and Vladimír Novák. "The preparation and stereochemistry of the ternary cobalt(III) complex of (2R,2'S)-2,2'-ethylene-bis(2-aminobutanoic) acid and ethylenediamine." Collection of Czechoslovak Chemical Communications 53, no. 4 (1988): 807–13. http://dx.doi.org/10.1135/cccc19880807.

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The ternary cobalt(III) complex [Co(EDDB)(en)]+ was prepared by oxidation of an aqueous solution of a cobalt(II) salt and the ligands by an equimolar amount of PbO2. Chromatographic separation on a cation exchanger yielded two geometric isomers, that were characterized by their electronic absorption, 13C NMR and IR spectra. Gel permeation chromatography was used to partially separate the two geometric isomers to yield the corresponding enantiomers, whose absolute configuration was found by CD.

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9

Lokesh, Sachin Rama Chaudhari, and N. Suryaprakash. "RES-TOCSY: a simple approach to resolve overlapped 1H NMR spectra of enantiomers." Organic & Biomolecular Chemistry 12, no. 6 (2014): 993. http://dx.doi.org/10.1039/c3ob42087f.

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10

Liu, Xiujun, Xiang Ma та Yaqing Feng. "Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction". Beilstein Journal of Organic Chemistry 15 (28 червня 2019): 1434–40. http://dx.doi.org/10.3762/bjoc.15.143.

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Isoxazoline-linked porphyrins have been synthesized by a regioselective 1,3-dipolar cycloaddition reaction between vinylporphyrin 2 and nitrile oxides. The steric interaction directed the reaction trajectory, in which only the product with a link between the 5-position of the isoxazoline and the β-position of porphyrin was observed. The isoxazoline-porphyrins 3a,b have been characterized by absorption, emission, 1H NMR and mass spectra. Later, the crystal structure of 3a was obtained and confirmed the basic features of the NMR-derived structure. Furthermore, a pair of enantiomers of 3a present

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11

Nguyen, Quang Trung, Phuong Nam Pham Thi, and Van Tuyen Nguyen. "Synthesis, Characterization, and In Vitro Cytotoxicity of Platinum(II) Complexes Bearing Chiral Tetradentate Salicylaldimine Ligands." Journal of Chemistry 2020 (June 16, 2020): 1–10. http://dx.doi.org/10.1155/2020/5414959.

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A series of platinum(II) complexes with chiral Schiff base ligands derived from various salicylaldehydes with (R,R′)- and (S,S′)-cyclohexanediamine were synthesized and characterized by ESI-MS, IR, and NMR. Obtained spectra with typical signals were in agreement with suggested molecular formulae of the complexes. Their photophysical properties were studied by UV-visible and emission spectroscopies. The UV-Vis showed the typical band with low energy at visible range 400–500 nm for MLCT, and this band can emit the luminescent band with emission maximum wavelengths at 529–595 nm. The in vitro cyt

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12

Jubert, Alicia H., María L. Alegre, Reinaldo Pis Diez, Alicia B. Pomilio, and Víctor D. Szewczuk. "Vibrational spectra, NMR and theoretical studies of the enantiomers and rotamers of alpha-cypermethrin." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 66, no. 4-5 (2007): 1208–21. http://dx.doi.org/10.1016/j.saa.2006.06.017.

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13

Ali, Muhammad Shaiq, Tomoya Kitazume, and Viqar Uddin Ahmad. "Enzymatic Racemic Resolution of a Fluorinated Substrate and Syntheses of E and Z Alkenes as Precursors for Some Biologically Active Fluorohexoses." Zeitschrift für Naturforschung B 52, no. 3 (1997): 413–18. http://dx.doi.org/10.1515/znb-1997-0320.

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Abstract A fluorinated substrate 6 was prepared and then the enantiomers (6a and 7a) were separated by an enzyme in presence of an acetylating agent. The optical purity of 6a and 7a were determined by derivatising them into their MTPA -esters and then by taking their 19F NMR spectra. It was observed that, PL 266 (enzyme), benzene (solvent), 24 h (time), 40 °C (temp.) and vinyl acetate (acetylating agent) were the ideal conditions for racemic resolution. The optical purity was further improved by changing the solvent (hexane), amount of enzyme (PL 266; 3000 units), reaction time (12 h) and amou

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14

Ukrainets, Igor V., Ganna M. Hamza, Anna A. Burian та ін. "The Crystal Structure of N-(1-Arylethyl)-4-methyl- 2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamides as the Factor Determining Biological Activity Thereof". Scientia Pharmaceutica 87, № 2 (2019): 10. http://dx.doi.org/10.3390/scipharm87020010.

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In order to detect new structural and biological patterns in a series of hetaryl-3-carboxylic acid derivatives, the optically pure (S)- and (R)-enantiomers of N-(1-arylethyl)-4-methyl- 2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxamides, their true racemates, and mechanical racemic mixtures have been synthesized in independent ways. The particular features of the 1Н- and 13С-NMR spectra of all synthesized substances, liquid chromato-mass spectrometric behavior thereof under electrospray ionization conditions, and also the results of polarimetric and X-ray diffraction studies have been discussed. P

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15

Hebbar, Sankeerth, Uday Ramesh Prabhu, and N. Suryaprakash. "Selective double quantum resolved correlation experiment for the complete separation of entire proton NMR spectra of enantiomers." Journal of Magnetic Resonance 215 (February 2012): 23–26. http://dx.doi.org/10.1016/j.jmr.2011.12.008.

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16

Prabhu, Uday Ramesh, Bikash Baishya, and N. Suryaprakash. "Separation and Complete Analyses of the Overlapped and Unresolved1H NMR Spectra of Enantiomers by Spin Selected Correlation Experiments." Journal of Physical Chemistry A 112, no. 25 (2008): 5658–69. http://dx.doi.org/10.1021/jp7102462.

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17

Prabhu, Uday Ramesh, Bikash Baishya, and N. Suryaprakash. "Chemical shift anisotropy edited complete unraveling of overlapped 1H NMR spectra of enantiomers: Application to small chiral molecules." Journal of Magnetic Resonance 191, no. 2 (2008): 259–66. http://dx.doi.org/10.1016/j.jmr.2007.12.019.

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18

Merlet, Denis, William Smadja, Jacques Courtieu, Philippe Lesot, and Bernard Ancian. "Analysis of natural abundance deuterium NMR spectra of enantiomers in chiral liquid crystals via 2D auto-correlation experiments." Chemical Communications, no. 21 (1998): 2301–2. http://dx.doi.org/10.1039/a805020a.

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19

Cholli, Ashok L., and Miu-Ling Lau. "Simultaneous Detection of Optical Isomers and the Separation of Overlapping Resonances in a 1H NMR Spectrum of (+/-)-2,2-Dimethyl-1-Phenyl-1-Propanol Using an NMR Shift Reagent." Applied Spectroscopy 43, no. 7 (1989): 1168–72. http://dx.doi.org/10.1366/0003702894203471.

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The enantiomer separation and the spectral simplification of overlapped resonances in a high-resolution 1H NMR spectrum of a model compound have been successfully accomplished with the use of paramagnetic shift reagent. Both 1H and 13C NMR have been applied to determine the composition of a mixture containing optically active enantiomers of (+/-)-2,2-dimethyl-1-phenyl-1-propanol.

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20

Lesot, P., D. Merlet, J. Courtieu, and J. W. Emsley. "Discrimination and analysis of the NMR spectra of enantiomers dissolved in chiral liquid crystal solvents through 2D correlation experiments." Liquid Crystals 21, no. 3 (1996): 427–35. http://dx.doi.org/10.1080/02678299608032851.

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21

Li, Tuo, Xue Ma, Daniil Fedotov, et al. "Structure Elucidation of Prenyl- and Geranyl-Substituted Coumarins in Gerbera piloselloides by NMR Spectroscopy, Electronic Circular Dichroism Calculations, and Single Crystal X-ray Crystallography." Molecules 25, no. 7 (2020): 1706. http://dx.doi.org/10.3390/molecules25071706.

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Crude ethyl acetate extract of Gerbera piloselloides (L.) Cass. was investigated by dual high-resolution PTP1B/α-glucosidase inhibition profiling and LC-PDA-HRMS. This indicated the presence of a series of unprecedented prenyl- and geranyl-substituted coumarin derivatives correlated with both α-glucosidase and PTP1B inhibitory activity. Repeated chromatographic separation targeting these compounds led to the isolation of 13 new compounds, of which ten could be isolated as both enantiomers after chiral separation. The structures of all isolated compounds were characterized by HRMS and extensive

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22

Donahue, Matthew G., and Emily Crull. "(R)-(+)-3,5-Dinitro-N-(1-phenylethyl)benzothioamide." Molbank 2023, no. 2 (2023): M1650. http://dx.doi.org/10.3390/m1650.

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(R)-(+)-3,5-dinitro-N-(1-phenylethyl)benzothioamide 1 is a potential chiral solvating agent (CSA) for the spectral resolution of enantiomers via 1H NMR spectroscopy. The single enantiomer of 1 was synthesized from commercially available (R)-(+)-a-methylbenzylamine 2 in two steps with 85% yield.

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23

MERLET, D., B. ANCIAN, W. SMADJA, J. COURTIEU, and P. LESOT. "ChemInform Abstract: Analysis of Natural Abundance Deuterium NMR Spectra of Enantiomers in Chiral Liquid Crystals via 2D Auto-correlation Experiments." ChemInform 30, no. 7 (2010): no. http://dx.doi.org/10.1002/chin.199907021.

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24

Beguin, Laetitia, Jacques Courtieu, Latifa Ziani, and Denis Merlet. "Simplification of the1H NMR spectra of enantiomers dissolved in chiral liquid crystals, combining variable angle sample spinning and selective refocusing experiments." Magnetic Resonance in Chemistry 44, no. 12 (2006): 1096–101. http://dx.doi.org/10.1002/mrc.1905.

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25

Weiss, Robin, Emmanuel Aubert, Paola Peluso, Sergio Cossu, Patrick Pale, and Victor Mamane. "Chiral Chalcogen Bond Donors Based on the 4,4′-Bipyridine Scaffold." Molecules 24, no. 24 (2019): 4484. http://dx.doi.org/10.3390/molecules24244484.

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Organocatalysis through chalcogen bonding (ChB) is in its infancy, as its proof-of-principle was only reported in 2016. Herein, we report the design and synthesis of new chiral ChB donors, as well as the catalytic activity evaluation of the 5,5′-dibromo-2,2′-dichloro-3-((perfluorophenyl)selanyl)-4,4′-bipyridine as organocatalyst. The latter is based on the use of two electron-withdrawing groups, a pentafluorophenyl ring and a tetrahalo-4,4′-bipyridine skeleton, as substituents at the selenium center. Atropisomery of the tetrahalo-4,4′-bipyridine motif provides a chiral environment to these new

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26

Baishya, Bikash, Uday Ramesh Prabhu, and N. Suryaprakash. "Spin state selective coherence transfer: A method for discrimination and complete analyses of the overlapped and unresolved 1H NMR spectra of enantiomers." Journal of Magnetic Resonance 192, no. 1 (2008): 101–11. http://dx.doi.org/10.1016/j.jmr.2008.02.005.

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27

Prabhu, Uday Ramesh, and N. Suryaprakash. "Selective Homonuclear Decoupling in1H NMR: Application to Visualization of Enantiomers in Chiral Aligning Medium and Simplified Analyses of Spectra in Isotropic Solutions." Journal of Physical Chemistry A 114, no. 17 (2010): 5551–57. http://dx.doi.org/10.1021/jp1013994.

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28

Garda, Zoltán, Tamara Kócs, István Bányai та ін. "Complexes of Bifunctional DO3A-N-(α-amino)propinate Ligands with Mg(II), Ca(II), Cu(II), Zn(II), and Lanthanide(III) Ions: Thermodynamic Stability, Formation and Dissociation Kinetics, and Solution Dynamic NMR Studies". Molecules 26, № 16 (2021): 4956. http://dx.doi.org/10.3390/molecules26164956.

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The thermodynamic, kinetic, and structural properties of Ln3+ complexes with the bifunctional DO3A-ACE4− ligand and its amide derivative DO3A-BACE4− (modelling the case where DO3A-ACE4− ligand binds to vector molecules) have been studied in order to confirm the usefulness of the corresponding Gd3+ complexes as relaxation labels of targeted MRI contrast agents. The stability constants of the Mg2+ and Ca2+ complexes of DO3A-ACE4− and DO3A-BACE4− complexes are lower than for DOTA4− and DO3A3−, while the Zn2+ and Cu2+ complexes have similar and higher stability than for DOTA4− and DO3A3− complexes

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29

Teng, Fei, Jianbo Ji, Yue Yang, and Haina Wang. "A useful quantitative model for determining the optical purity of praziquantel enantiomers based on near infrared spectroscopy with partial least squares." Journal of Near Infrared Spectroscopy 30, no. 5 (2022): 246–53. http://dx.doi.org/10.1177/09670335221130428.

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In this study, a new method was developed for the determination of praziquantel (PZQ) enantiomers in solution. Praziquantel, as a highly effective and low-toxic broad-spectrum antiparasitic drug developed in the 1970s, is the first choice for the etiology of schistosomiasis treatment recommended by the World Health Organization. It is by far the most effective anti-schistosomiasis drug. PZQ is a chiral drug with a chiral carbon atom and two enantiomers, of which R-PZQ is the main contributor of the anti-schistosome effect. The quantitative model was established based on near infrared (NIR) spe

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30

Krasnov, Victor P., Vera V. Musiyak, Galina L. Levit, et al. "Synthesis of Pyrimidine Conjugates with 4-(6-Amino-hexanoyl)-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine and Evaluation of Their Antiviral Activity." Molecules 27, no. 13 (2022): 4236. http://dx.doi.org/10.3390/molecules27134236.

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A series of pyrimidine conjugates containing a fragment of racemic 7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine and its (S)-enantiomer attached via a 6-aminohexanoyl fragment were synthesized by the reaction of nucleophilic substitution of chlorine in various chloropyrimidines. The structures of the synthesized compounds were confirmed by 1H, 19F, and 13C NMR spectral data. Enantiomeric purity of optically active derivatives was confirmed by chiral HPLC. Antiviral evaluation of the synthesized compounds has shown that the replacement of purine with a pyrimidine fragment leads to a dec

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31

Hatzis, Alexander, and Robert Rothchild. "1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Part III:* Vinclozolin." Applied Spectroscopy 40, no. 6 (1986): 743–45. http://dx.doi.org/10.1366/0003702864508359.

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The 60 MHz 1H NMR spectra of racemic vinclozolin, 1, have been studied at 28° in CDCI3 solution with the achiral reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)- d-camphorato] europium(III), 3, and tris[3-(heptafluoropropylhydroxymethylene)- d-camphorato]europium(III), 4. Reagent 3 produced only small lanthanide-induced shifts and no observable enantiomeric shift differences, ΔΔδ, with 3:1 molar ratios as high as 1.40. In contrast, chiral reagent 4 produced substantial ΔΔδ for the proton, H

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32

Merelli, Bérangère, Laurence Menguy, Estelle Soubeyrand-Lenoir, and Jean-Claude Cherton. "Determination of the enantiomeric composition of chiral delta-2-thiazolines-1,3 by1H and19F NMR spectroscopy using chiral solvating agents." Spectroscopy 20, no. 3 (2006): 95–107. http://dx.doi.org/10.1155/2006/698685.

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Studies of the perturbing effect of chiral solvating agents (CSAs) namely the fluoroalcohols5aand5bupon the NMR spectra of chiral Δ2-thiazolines1presenting interesting insecticidal properties demonstrated the ability of these CSAs to afford diastereomeric solvates from these substrates providing their enantiomeric discrimination. Thus, for five of the six tested Δ2-thiazolines1Aand1Bthere is at least one possibility to proceed to their enantiomeric discrimination either by1H or19F NMR using mostly5bas CSA.

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33

Berdagué, Philippe, Jose-Enrique Herbert-Pucheta, Vishwajeet Jha, Armen Panossian, Frédéric R. Leroux, and Philippe Lesot. "Multi-nuclear NMR of axially chiral biaryls in polypeptide orienting solvents: spectral discriminations and enantiorecognition mechanisms." New Journal of Chemistry 39, no. 12 (2015): 9504–17. http://dx.doi.org/10.1039/c5nj01434d.

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34

Biancolillo, Alessandra, Stefano Battistoni, Regina Presutto, and Federico Marini. "Green Multi-Platform Solution for the Quantification of Levodopa Enantiomeric Excess in Solid-State Mixtures for Pharmacological Formulations." Molecules 26, no. 16 (2021): 4944. http://dx.doi.org/10.3390/molecules26164944.

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The aim of the present work was to develop a green multi-platform methodology for the quantification of l-DOPA in solid-state mixtures by means of MIR and NIR spectroscopy. In order to achieve this goal, 33 mixtures of racemic and pure l-DOPA were prepared and analyzed. Once spectra were collected, partial least squares (PLS) was exploited to individually model the two different data blocks. Additionally, three different multi-block approaches (mid-level data fusion, sequential and orthogonalized partial least squares, and sequential and orthogonalized covariance selection) were used in order

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35

Chen, Jian-Xin, Shen-Hui Huang, Lei Wang, et al. "Two Pairs of Enantiomeric Neolignans from Lobelia Chinensis." Natural Product Communications 5, no. 10 (2010): 1934578X1000501. http://dx.doi.org/10.1177/1934578x1000501023.

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A pair of new enantiomeric neolignans, ethyl 3-[(2 R,3 S)-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-7-methoxy-2,3-dihydro-1-benzofuran-5-yl] propanoate (+) (1) and ethyl 3-[(2 S,3 R)-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-7-methoxy-2,3-dihydro-1-benzofuran-5-yl] propanoate (-) (1), together with a pair of known enantiomeric neolignans (+) (2) and (-) (2), as well as five known lignans (3-7) were isolated from the ethanol extract of Lobelia chinensis. Their structures were elucidated on the basis of extensive spectroscopic analyses, including 1D and 2D NMR, HR-ESIMS and CD spectr

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36

Zakia Afzal, Zakia Afzal, and Naghmana Rashid and Humaira Nadeem Naghmana Rashid and Humaira Nadeem. "Stereoselective Synthesis, Spectral Characterization, Docking and Biological Screening of Coumarin Derivatives." Journal of the chemical society of pakistan 43, no. 3 (2021): 330. http://dx.doi.org/10.52568/000580/jcsp/43.03.2021.

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The compounds being synthesized in present research are chiral in nature so for getting enantiopure compounds, stereoselective synthesis was carried out by organocatalysis. The importance of enantiopure compounds can not be overstated because the living systems are chiral in nature and response of enantiomers can be very different in living systems. The organocatalysed synthesis was accumplished using 4-hydroxycoumarin and variously substituted dibenzylideneacetones as reactants and the organocatalyst being used was 9-amino-9-deoxyepiquinine. The range of enantioselectivity achieved was 24-95%

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Zakia Afzal, Zakia Afzal, and Naghmana Rashid and Humaira Nadeem Naghmana Rashid and Humaira Nadeem. "Stereoselective Synthesis, Spectral Characterization, Docking and Biological Screening of Coumarin Derivatives." Journal of the chemical society of pakistan 43, no. 3 (2021): 330. http://dx.doi.org/10.52568/000580.

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The compounds being synthesized in present research are chiral in nature so for getting enantiopure compounds, stereoselective synthesis was carried out by organocatalysis. The importance of enantiopure compounds can not be overstated because the living systems are chiral in nature and response of enantiomers can be very different in living systems. The organocatalysed synthesis was accumplished using 4-hydroxycoumarin and variously substituted dibenzylideneacetones as reactants and the organocatalyst being used was 9-amino-9-deoxyepiquinine. The range of enantioselectivity achieved was 24-95%

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Jadhav, D. N., P. Nag, R. S. Lokhande, J. G. Chandorkar, and S. K. Sharma. "APPLICATION OF TARTARIC ACID DERIVATIVES IN ENANTIOSEPARATION OF RS-IBUPROFEN." RASAYAN Journal of Chemistry 15, no. 02 (2022): 1461–68. http://dx.doi.org/10.31788/rjc.1526875.

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A novel Tartaric acid derivative-based chiral resolving agent has been discovered for the enantiosepration of racemic Ibuprofen [(RS)-2-(4-(2-methyl propyl) phenyl) propanoic acid]. The processinvolves optimization of diastereomeric salt formed between (+) Ibuprofen and optically pure tartaric acid derivatives, followed by separating the individual enantiomer by acid salt preparation. Characterization of the synthesized compound has been carried out by elemental analysis, melting point, FT-IR, UV, HPLC, and 1H NMR spectra. The developed separation method is simple, cost-effective, and industri

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Puentes, Cira Mollings, and Thomas J. Wenzel. "Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds." Beilstein Journal of Organic Chemistry 13 (January 6, 2017): 43–53. http://dx.doi.org/10.3762/bjoc.13.6.

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The utility of phosphated α-, β- and γ-cyclodextrins as water-soluble chiral NMR solvating agents for cationic substrates is described. Two sets of phosphated cyclodextrins, one with degrees of substitution in the 2–6 range, the other with degrees of substitution in the 6–10 range, are examined. Results with 33 water-soluble cationic substrates are reported. We also explored the possibility that the addition of paramagnetic lanthanide ions such as praseodymium(III) and ytterbium(III) further enhances the enantiomeric differentiation in the NMR spectra. The chiral differentiation with the phosp

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Prata, José V., Patrícia D. Barata, and Gennaro Pescitelli. "Inherently chiral calix[4]arenes with planar chirality: two new entries to the family." Pure and Applied Chemistry 86, no. 11 (2014): 1819–28. http://dx.doi.org/10.1515/pac-2014-0707.

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Abstract The synthesis of two new inherently chiral calix[4]arenes (ICCs, 1 and 2), endowed with electron-rich concave surfaces, has been achieved through the desymmetrization of a lower rim distal-bridged oxacyclophane (OCP) macrocycle. The new highly emissive ICCs were resolved by chiral HPLC, and the enantiomeric nature of the isolated antipodes proved by electronic circular dichroism (CD). Using time-dependent density functional calculations of CD spectra, their absolute configurations were established. NMR studies with (S)-Pirkle’s alcohol unequivocally showed that the host-guest interact

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41

Gorina, Svetlana S., Alevtina M. Egorova, Natalia V. Lantsova, Yana Y. Toporkova та Alexander N. Grechkin. "Discovery of α-Linolenic Acid 16(S)-Lipoxygenase: Cucumber (Cucumis sativus L.) Vegetative Lipoxygenase 3". International Journal of Molecular Sciences 24, № 16 (2023): 12977. http://dx.doi.org/10.3390/ijms241612977.

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The GC-MS profiling of the endogenous oxylipins (Me/TMS) from cucumber (Cucumis sativus L.) leaves, flowers, and fruit peels revealed a remarkable abundance of 16-hydroxy-9,12,14-octadecatrienoic acid (16-HOT). Incubations of homogenates from these organs with α-linolenic acid yielded 16(S)-hydroperoxide (16-HPOT) as a predominant product. Targeted proteomic analyses of these tissues revealed the presence of several highly homologous isoforms of the putative “9S-lipoxygenase type 6”. One of these isoenzymes (CsLOX3, an 877 amino acid polypeptide) was prepared by heterologous expression in E. c

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42

Plainchont, Bertrand, Daisy Pitoux, Mathieu Cyrille, and Nicolas Giraud. "Highly Accurate Quantitative Analysis Of Enantiomeric Mixtures from Spatially Frequency Encoded1H NMR Spectra." Analytical Chemistry 90, no. 3 (2018): 1595–600. http://dx.doi.org/10.1021/acs.analchem.7b02411.

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43

Labuta, Jan, Shinsuke Ishihara, and Jonathan P. Hill. "meso-Tetraphenylporphine as a prochiral solvating agent (pro-CSA): A physicochemical study." Journal of Porphyrins and Phthalocyanines 24, no. 01n03 (2020): 320–29. http://dx.doi.org/10.1142/s1088424619501141.

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Meso-tetraphenylporphine (TPP) can be used as a prochiral chiral solvating agent (pro-CSA) for NMR detection of enantiomeric excess (ee) of chiral organic acids, in this study 2-phenoxypropionic acid (PPA). The pro-CSA sensing mechanism is unique in that it does not depend on formation of diastereomers. Here we discuss the factors affecting construction of the calibration curves ([Formula: see text] observed linearity between induced chemical shift non-equivalency and ee) including temperature, guest exchange rate and binding strength. We have employed various NMR techniques including variable

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44

Mynott, Richard, Wolf Jürgen Richter та Günther Wilke. "Determination of the Enantiomeric Excess of Horner Phosphines by 13C NMR Spectroscopy. A 13C and 31P NMR Study of the Diastereomeric Complexes Formed with [η3-(+)(1R,5R )-Pinenyl]nickel Bromide Dimer". Zeitschrift für Naturforschung B 41, № 1 (1986): 85–88. http://dx.doi.org/10.1515/znb-1986-0118.

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The 13C and 31P NMR data of the Horner phosphines PRR′R″ [R = Me. R′ = t-Bu, R'″ = Ph (2) or i-Pr (4)] and their diastereomeric 1:1 adducts with [η3-(+)(1 R, 5 R)-pinenyI]nickel bromide dimer (3) and (5), respectively, are reported. It is shown that the optical purities of the phosphines can be deduced easily from the NMR spectra. Not only are these values in very good agreement with those obtained from optical rotatory data but they are also obtained much more conveniently.

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Farjon, Jonathan, Jean-Pierre Baltaze, Philippe Lesot, Denis Merlet, and Jacques Courtieu. "Heteronuclear selective refocusing 2D NMR experiments for the spectral analysis of enantiomers in chiral oriented solvents." Magnetic Resonance in Chemistry 42, no. 7 (2004): 594–99. http://dx.doi.org/10.1002/mrc.1399.

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Fritsky, Igor O., Rostislav D. Lampeka, Victor V. Skopenko, Yury A. Simonov, Alexander A. Dvorkin, and Tadeusz I. Malinowsky. "Synthesis, Structure and Characterization of Trisodium Bis[N-(2-oximinopropionyl)glycinato(3 – )-O,N,N'] Cobaltate(III) Nonahydrate." Zeitschrift für Naturforschung B 48, no. 3 (1993): 270–76. http://dx.doi.org/10.1515/znb-1993-0304.

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A cobalt(III) complex with pyruvylglycine oxime (H3G) of composition Na3[CoG2] · 9 H2O is synthesized and investigated by means of X-ray analysis, infrared, electronic and NMR spectroscopy. The crystals are triclinic, space group P1̄, a = 15.477(5), b = 9.931(4), c = 7.773(4)Å; α = 75.60(3); β = 82.86(4); γ = 93.54(3)°; Ζ = 2. The structure was refined to final R = 0.036 for 3347 independent observed reflections. The structure consists of the complex anions, Na+ cations and water molecules. The ligands are coordinated via the deprotonated oxime and amide nitrogen and the carboxyl oxygen atoms

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47

Ryu, Min-Ji, Prima F. Hillman, Jihye Lee, et al. "Antibacterial Meroterpenoids, Merochlorins G–J from the Marine Bacterium Streptomyces sp." Marine Drugs 19, no. 11 (2021): 618. http://dx.doi.org/10.3390/md19110618.

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Four new chlorinated meroterpenoids, merochlorins G−J (1−4), and 10, a dihydronaphthalenedione precursor, along with known merochlorins A (5) and C−F (6−9), were obtained from cultivation of the bacterium strain Streptomyces sp. CNH-189, which was isolated from marine sediment. The planar structures of compounds 1−4 and 10 were elucidated by interpretation of MS, UV, and NMR spectroscopic data. The relative configurations of compounds 1−4 were determined via analysis of nuclear Overhauser effect (NOE) spectroscopic data, after which their absolute configurations were established by comparing t

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48

Grindley, T. Bruce, Paula J. MacLeod, James A. Pincock, and T. Stanley Cameron. "Conformational behaviour of highly hindered ethanes: meso- and racemic-2,2,2′,2′-tetramethyl-1,1′-biindanyl." Canadian Journal of Chemistry 74, no. 10 (1996): 1795–809. http://dx.doi.org/10.1139/v96-200.

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MM3(94), AM1, and STO-3G calculations on racemic 2,2,2′,2′-tetramethyl-1,1′-biindanyl (1) show that seven minima are present on its conformational potential energy surface. 1 crystallizes in the space group Pbcn (no. 60) with cell parameters a = 11.190(7), b = 11.679(7), c = 13.19(1) Å, V = 1724(3) Å3, Z = 4, R = 0.0357, Rw = 0.0362 in the conformation predicted to be the global minimum by STO-3G and AM1, but not by MM3(94). Application of the Karplus equation and observation of a deshielded proton signal indicate that the same conformation is the major species present in solution, perhaps alo

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49

Sabbaghi, Fahimeh, Mehrdad Pourayoubi, Marek Nečas, and Krishnan Damodaran. "Two single-enantiomer amidophosphoesters: a database study on the chirality of (O)2P(O)(N)-based structures." Acta Crystallographica Section C Structural Chemistry 75, no. 1 (2019): 77–84. http://dx.doi.org/10.1107/s205322961801673x.

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The crystal structures of two single-enantiomer amidophosphoesters with an (O)2P(O)(N) skeleton, i.e. diphenyl [(R)-(+)-α-methylbenzylamido]phosphate, (I), and diphenyl [(S)-(−)-α-methylbenzylamido]phosphate, (II), both C20H20NO3P, are reported. In both structures, chiral one-dimensional hydrogen-bonded architectures, along [010], are mediated by N—H...OP interactions. The statistically identical assemblies include the noncentrosymmetric graph-set motif C(4) and the compounds crystallize in the chiral space group P21. As a result of synergistic co-operation from C—H...O interactions, a two-dim

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Wang, Wen-Qing, Wei Min, Zhi Liang, Li-Ying Wang, Lei Chen, and Feng Deng. "NMR and parity violation: low-temperature dependence in 1H CRAMPS and 13C CP/MAS ssNMR spectra of alanine enantiomer." Biophysical Chemistry 103, no. 3 (2003): 289–98. http://dx.doi.org/10.1016/s0301-4622(02)00320-4.

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